Tuesday, August 6, 2013

New paper finds Antarctic sea ice retreated during the 1940's when CO2 was 'safe' & not since

A new paper published in Quaternary Science Reviews reconstructs sea ice changes around the Antarctic Peninsula from 1860-2000 and finds "abrupt changes between 1935 and 1950, marked by ocean warming and sea ice retreat in both sides of the Antarctic Peninsula." However, the authors find that from 1950-2000 there was no trend in sea ice extent, stating, "Since 1950, inferred environmental conditions do not provide evidence for any trend related to the recent warming". Satellite data, available since 1979, shows Antarctic sea ice is currently at record highs, 900,000 square kilometers above the 1979-2008 average. If man-made CO2 emissions had anything to do with Antarctic sea ice, the opposite pattern would have been observed over the past 153 years.

Notes: Global sea ice is also currently above the 1979-2008 mean. The Antarctic Peninsula isfalsely claimed to be one of the most rapidly warming regions on Earth.

Abstract

The Antarctic Peninsula (AP) has been identified as one of the most rapidly warming region on Earth. Satellite monitoring currently allows for a detailed understanding of the relationship between sea ice extent and duration and atmospheric and oceanic circulations in this region. However, our knowledge on ocean–ice–atmosphere interactions is still relatively poor for the period extending beyond the last 30 years. Here, we describe environmental conditions in Northwestern and Northeastern Antarctic Peninsula areas over the last century using diatom census counts and diatom specific biomarkers (HBIs) in two marine sediment multicores (MTC-38C and -18A, respectively). Diatom census counts and HBIs show abrupt changes between 1935 and 1950, marked by ocean warming and sea ice retreat in both sides of the AP. Since 1950, inferred environmental conditions do not provide evidence for any trend related to the recent warming but demonstrate a pronounced variability on pluri-annual to decadal time scale. We propose that multi-decadal sea ice variations over the last century are forced by the recent warming, while the annual-to-decadal variability is mainly governed by synoptic and regional wind fields in relation with the position and intensity of the atmospheric low-pressure trough around the AP. However, the positive shift of the SAM since the last two decades cannot explain the regional trend observed in this study, probably due to the effect of local processes on the response of our biological proxies.